We synthesized and characterized gold nanostars and their silica-coated derivatives with 7- to 50-nm shell thicknesses as contrast agents for optical imaging. The scattering and absorption coefficients of the nanoparticles (NPs) were estimated by means of collimated transmittance and diffuse reflectance/transmittance analyses. The contrasting properties of the nanostructures were studied in optical coherence tomography glass capillary imaging. The silica-coated nanostars with the thickest shell have higher scattering ability in comparison with bare nanostars. Viability assays confirmed weak in vitro toxicity of nanostructures at up to ∼200-μg/mL concentrations. We showed real-time visualization of nanostars in both agarose and cultured cells by analyzing the backscattering signal using a conventional laser confocal microscope. The signal intensity detected from the silica-coated NPs was almost 1.5 times higher in comparison with bare nanostars. To the best of our knowledge, this is the first time that conventional laser confocal microscopy was applied in combined scattering and transmitted light modes to detect the backscattered signal of gold nanostars, which is useful for direct monitoring of the uptake, translocation, and accumulation of NPs in living cells.
In this paper, an overview of selected applications of semiconductor (TiO2 and ZnO) and upconversion nanoparticles is presented. Depending on the size, the former are used as scattering and absorbing compounds in sunscreens and tissuemimicking phantoms; and in combination with gypsum – also as an antibacterial coating for indoor premises, while the latter, especially in combination with optical clearing – as a promising component for deep-biotissue imaging both in vitro and in vivo.
In this paper, plasmon-resonant nanostructures, such as gold nanostars and their silica-coated composites, were used for enhancement of OCT image contrast of water flows in glass capillaries. The contrasting properties of the synthesized nanostars and nanocomposites with silica shell thickness of about 5 nm and 50 nm were compared in the framework of capillary stasis model. The most intensive signal was detected from the nanocomposites with the thickest silica shell. The nanocomposites were characterized by optical spectroscopy and electron microscopy. Nontoxicity of nanostars and nanocomposites up to ~ 3 mg/mL concentration was showed by MTT assay suggesting practical applications of the nanostructures for bioimaging.
In this work, two types of nanocomposites, silica-coated nano-sea-urchins and silica-coated gold nanostars, were
fabricated. CTAB-coated nano-sea-urchins with an average size of about 100 nm demonstrate an absorption peak near
600-700 nm and stability in aqueous suspension. CTAB was exchanged with m-PEG-SH by an intermediate PEG layer.
A layer of silica was synthesized on the nano-sea-urchins surface with thickness of about 20 nm. Nanostars with an
average size of about 60 nm with a number of thin sharp branches were fabricated and functionalized by PVP to improve
their stability. PVP-coated nanostars were used in optical coherence tomography experiments to show their contrasting
properties. After silica-coating, stable and monodispersed nanoparticles with silica shell thickness about 60 nm were
obtained. Nontoxicity of the silica-coated nanostars at least until the concentration of nanoparticles about 400 μg/mL was
showed by fluorescent cell viability assay using propidium iodide. Extinction coefficient of the gold nanostars and
nanocomposites was estimated by a spectrophotometer system in collimated transmission regime.
Thin films of functionalized single-wall carbon nanotubes were deposited on silicon chips by drop-coating and inkjet printing. These sensors were subjected to 1-100 ppm NOx, CO, H2S and H2O vapor in synthetic air. We have found that besides the expected changes in the electrical resistance of the film, there are also characterteristic differences in the noise pattern of the resistance vs. time function. This phenomenon is called fluctuation enhanced sensing and it can be used to increase the amount of information gathered from a carbon nanotube sensor device. The main advantage of fluctuation enhanced sensing is the improved selectivity of the sensor even if changes in electical resistance are rather low. Combined with differentiation based on modifying the adsorption characterstics of the nanotubes (e.g. by covalent functionalization), fluctuation enhanced sensing appears to be a very useful method for bringing cheap and reliable carbon nanotube based chemical sensors to the market.
Low temperature co-fired ceramics (LTCCs) are mainly applied in hybride microelectronics packaging technology, whereas the fabrication of metallic conductors on LTCC materials is done by various printing technologies. The conventional process is fast and cost-effective in the case of mass-production but too slow and difficult when repair and/or some modifications in circuitry are needed. Printing also fails when deposition of thin metal films on LTCC is demanded. Here, a simple laser-assisted process is presented by which the surface of LTCCs can be activated for consecutive electroless chemical metal plating. The method enables the realization of thick high-conductance metallic Cu micro-patterns and thin seed layers of Ag and Au, with a lateral resolution of a few tens of micrometers. The process is also suitable for 3D-MEMS applications. Morphological, structural and composition aspects of LTCC surfaces treated by a Nd:YAG pulses are carried out using FESEM, SEM, XRD and Raman measurements.
12 A review of results of a last few years investigation in the field of laser light induced liquid phase metal deposition on different substrates is presented. The role of liquid phase chemical deposition techniques represents a certain interest for contemporary micro technology because of its technical and economical advantages compared to other technics e.g. chemical vapor phase deposition. The methods do not require harmful precursors, complicated vacuum tools, and it is cost effective.